It's no secret that radiation is harmful. Everyone knows this. Everyone has heard about the terrible casualties and the dangers of radioactive exposure. What is radiation? How does it arise? Are there different types of radiation? And how to protect yourself from it?
The word "radiation" comes from the Latin radius and denotes a ray. In principle, radiation is all types of radiation existing in nature - radio waves, visible light, ultraviolet and so on. But there are different types of radiation, some of them are useful, some are harmful. In ordinary life, we are accustomed to using the word radiation to refer to harmful radiation resulting from the radioactivity of certain types of substances. Let's look at how the phenomenon of radioactivity is explained in physics lessons.
Radioactivity in physics
We know that atoms of matter consist of a nucleus and electrons rotating around it. So the core is, in principle, a very stable formation that is difficult to destroy. However, the atomic nuclei of some substances are unstable and can emit various energies and particles into space.
This radiation is called radioactive, and it includes several components, which are named according to the first three letters of the Greek alphabet: α-, β- and γ- radiation. (alpha, beta and gamma radiation). These radiations are different, and their effect on humans and measures to protect against it are also different. Let's look at everything in order.
Alpha radiation
Alpha radiation is a stream of heavy, positively charged particles. Occurs as a result of the decay of atoms of heavy elements such as uranium, radium and thorium. In the air, alpha radiation travels no more than five centimeters and, as a rule, is completely blocked by a sheet of paper or the outer dead layer of skin. However, if a substance that emits alpha particles enters the body through food or air, it irradiates internal organs and becomes dangerous.
Beta radiation
Beta radiation is electrons that are much smaller than alpha particles and can penetrate several centimeters deep into the body. You can protect yourself from it with a thin sheet of metal, window glass, and even ordinary clothing. When beta radiation reaches unprotected areas of the body, it usually affects the upper layers of the skin. During the Chernobyl nuclear power plant accident in 1986, firefighters suffered skin burns as a result of very strong exposure to beta particles. If a substance that emits beta particles enters the body, it will irradiate internal tissues.
Gamma radiation
Gamma radiation is photons, i.e. electromagnetic wave carrying energy. In the air it can travel long distances, gradually losing energy as a result of collisions with atoms of the medium. Intense gamma radiation, if not protected from it, can damage not only the skin, but also internal tissues. Dense and heavy materials such as iron and lead are excellent barriers to gamma radiation.
As you can see, according to its characteristics, alpha radiation is practically not dangerous if you do not inhale its particles or eat them with food. Beta radiation can cause skin burns due to exposure. Gamma radiation has the most dangerous properties. It penetrates deep into the body, and it is very difficult to remove it from there, and the effects are very destructive.
In any case, without special instruments, it is impossible to know what type of radiation is present in this particular case, especially since you can always accidentally inhale radiation particles in the air. Therefore, there is only one general rule - to avoid such places, and if you find yourself, then wrap yourself in as much clothing and things as possible, breathe through the fabric, do not eat or drink, and try to leave the place of infection as quickly as possible. And then, at the first opportunity, get rid of all these things and wash yourself thoroughly.
Radioactivity can also be seen as evidence of the complex structure of atoms. Initially, ancient philosophers imagined the smallest particle of matter - an atom - as an indivisible particle. How did radioactivity destroy this idea? Details at the link.
>> Alpha, beta and gamma radiation
§ 99 ALPHA, BETA AND GAMMA RADIATIONS
After the discovery of radioactive elements, research began into the physical nature of their radiation. In addition to Becquerel and the Curies, Rutherford took up this task.
The classic experiment that made it possible to detect the complex composition of radioactive radiation was as follows. The radium preparation was placed at the bottom of a narrow channel in a piece of lead. There was a photographic plate opposite the channel. The radiation emerging from the channel was affected by a strong magnetic field, the induction lines of which were perpendicular to the beam (Fig. 13.6). The entire installation was placed in a vacuum.
In the absence of a magnetic field, one dark spot was detected on the photographic plate after development exactly opposite the channel. In a magnetic field, the beam split into three beams. The two components of the primary flow were deflected in opposite directions. This indicated that these radiations had electrical charges of opposite signs. In this case, the negative component of the radiation was deflected by the magnetic field much more strongly than the positive one. The third component was not deflected by the magnetic field at all. The positively charged component is called alpha rays, the negatively charged component is called beta rays, and the neutral component is called gamma rays (-rays, -rays, -rays).
These three types of radiation differ greatly in penetrating ability, that is, in how intensely they are absorbed by various substances. -rays have the least penetrating ability. A layer of paper about 0.1 mm thick is already opaque for them. If you cover a hole in a lead plate with a piece of paper, then no spot corresponding to -radiation will be found on the photographic plate.
Much less is absorbed when passing through matter - rays. The aluminum plate completely stops them only with a thickness of a few millimeters. .-rays have the greatest penetrating ability.
The intensity of absorption of -rays increases with increasing atomic number of the absorbent substance. But a layer of lead 1 cm thick is not an insurmountable obstacle for them. When β-rays pass through such a layer of lead, their intensity weakens only by half. The physical nature of -, - and - rays is obviously different.
Gamma rays. In their properties, rays are very similar to X-rays, but their penetrating power is much greater than that of X-rays. This suggested that the -rays were electromagnetic waves. All doubts about this disappeared after the diffraction of β-rays on crystals was discovered and their wavelength was measured. It turned out to be very small - from 10 -8 to 10 -11 cm.
On the scale of electromagnetic waves, -rays directly follow X-rays. The speed of propagation of y-rays is the same as that of all electromagnetic waves - about 300,000 km/s.
Beta rays. From the very beginning, - and - rays were considered as streams of charged particles. It was easiest to experiment with -rays, since they are more strongly deflected in both magnetic and electric fields.
The main task of the experimenters was to determine the charge and mass of the particles. When studying the deflection of -particles in electric and magnetic fields, it was found that they are nothing more than electrons moving at speeds very close to the speed of light. It is important that the velocities of -particles emitted by any radioactive element are not the same. There are particles with very different speeds. This leads to the expansion of the beam of particles in a magnetic field (see Fig. 13.6).
Alpha particles. It was more difficult to find out the nature of -particles, since they are less strongly deflected by magnetic and electric fields. Rutherford finally managed to solve this problem. He measured the ratio of a particle's charge q to its mass m by its deflection in a magnetic field. It turned out to be approximately 2 times less than that of a proton - the nucleus of a hydrogen atom. The charge of a proton is equal to the elementary one, and its mass is very close to the atomic mass unit 1. Consequently, the y-particle has a mass equal to two atomic mass units per elementary charge.
But the charge of the particle and its mass remained, nevertheless, unknown. It was necessary to measure either the charge or the mass of the particle. With the advent of the Geiger counter, it became possible to measure charge more easily and accurately. Through a very thin window, particles can penetrate into the counter and be registered by it.
Rutherford placed a Geiger counter in the path of the particles, which measured the number of particles emitted by a radioactive drug over a certain time. Then he replaced the counter with a metal cylinder connected to a sensitive electrometer (Fig. 13.7). Using an electrometer, Rutherford measured the charge - particles emitted by the source inside the cylinder in the same time (the radioactivity of many substances almost does not change with time). Knowing the total charge of the -particles and their number, Gezerfod determined the ratio of these quantities, i.e., the charge of one -particle. This charge turned out to be equal to two elementary ones.
Thus, he established that the y-particle has two atomic mass units for each of the two elementary charges. Therefore, there are four atomic mass units per two elementary charges. The helium nucleus has the same charge and the same relative atomic mass. It follows from this that a particle is the nucleus of a helium atom.
Not content with the achieved result, Rutherford then proved through direct experiments that it is helium that is formed during radioactive decay. Collecting -particles inside a special container for several days, he, using spectral analysis, was convinced that helium was accumulating in the vessel (each -particle captured two electrons and turned into a helium atom).
1 Atomic mass unit (a.s.m.) rapia 1/12 the mass of a carbon atom; 1 a. e.m. 1.66057 10 -27 kg.
During radioactive decay, -rays (nuclei of a helium atom), -rays (electrons) and -rays (short-wave electromagnetic radiation) are produced.
Why did it turn out to be much more difficult to find out the nature of -rays than in the case of -rays?
Myakishev G. Ya., Physics. 11th grade: educational. for general education institutions: basic and profile. levels / G. Ya. Myakishev, B. V. Bukhovtsev, V. M. Charugin; edited by V. I. Nikolaeva, N. A. Parfentieva. - 17th ed., revised. and additional - M.: Education, 2008. - 399 p.: ill.
Physics lesson planning online, tasks and answers by grade, physics homework for grade 11 download
Lesson content lesson notes supporting frame lesson presentation acceleration methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photographs, pictures, graphics, tables, diagrams, humor, anecdotes, jokes, comics, parables, sayings, crosswords, quotes Add-ons abstracts articles tricks for the curious cribs textbooks basic and additional dictionary of terms other Improving textbooks and lessonscorrecting errors in the textbook updating a fragment in a textbook, elements of innovation in the lesson, replacing outdated knowledge with new ones Only for teachers perfect lessons calendar plan for the year; methodological recommendations; discussion programs Integrated LessonsInvisible rays penetrate through all objects around and through ourselves. We do not perceive or feel them in any way. It is impossible to defend against them; they are elusive and pervasive. They can heal and they can kill, they can contribute to the birth of previously unseen creatures on earth and lead to the emergence of new star clusters in the distant corners of our galaxy.
All this is not a fragment of the ravings of a madman, taken from the history of his illness, and not a brief synopsis of another Hollywood action movie. This is the reality surrounding us, which is called radioactive or ionizing radiation, in short -.
The phenomenon of radioactivity was formulated in general terms by the French physicist A. Becquerel in 1896. E. Rutherford concretized this phenomenon and described it in more detail in 1899. It was he who was able to establish that radioactive radiation is heterogeneous in nature and consists of at least three types of rays. These rays were deflected differently in the magnetic field and therefore received different names. The penetrating power of alpha, beta and gamma radiation is different.
Everyday protection
One of the most effective ways of protection in everyday life is the use of so-called or individual dosimeters. This is especially true due to the fact that the human body is deprived of the ability to perceive radiation through the senses; it simply does not notice it. The following individual dosages are distinguished:
- Normal daily dose: 10−20 microroentgen per hour.
- Normal single dose: 100 microroentgen.
- Lethal dose: 600 roentgens. When receiving such a single dose of radiation, a person dies within one to two weeks.
It must be borne in mind that basic hand washing with clean water and soap is a prevention of radioactive contamination, since in this case, contaminated radioactive substances are effectively removed from the surface of the skin.
There is no need to try to open or disassemble randomly found objects with radiation markings. This is not only dangerous for your health and the health of others. It must be borne in mind that the Criminal Code has a corresponding article for intentional or accidental radioactive contamination, so it is better to immediately report a dangerous find to the relevant services.
1. What is the phenomenon of radioactivity?
In 1896, French physicist Henri Becquerel accidentally placed a piece of uranium ore on a stack of undeveloped photographic plates wrapped in black paper. Having developed the plates, he was surprised to find black spots on them. Some unknown radiation was emitted from the uranium ore and left an image on the plates in the shape of a piece of ore. This radiation was called radioactive .
Thus, called radioactivity the property of nuclei to spontaneously (i.e., without any external influences) decay with the formation of new elements and the emission of a special kind of radiation called radioactive radiation.
2. What is the nature of alpha, beta and gamma radiation?
Rutherford discovered that the radiation of radioactive substances is divided by a magnetic field into a weakly deflected beam of positively charged particles (α - particles) and a strongly deflected beam of negatively charged particles (β - particles). Subsequently, Paul Willard discovered another component of radiation - γ rays, which are emitted by radioactive sources and are not deflected by a magnetic field.
Alpha rays represent a stream of nuclei of helium atoms. An alpha particle consists of two protons and two neutrons and, accordingly, has an atomic number of 2 and a mass number of 4. This was proven by direct experiments by Rutherford and Soddy. Thus, radon gas, emitting α-rays, creates helium atoms in a closed vessel, which is detected by the radiation spectrum.
The initial speed of alpha particles is of the order of (1.5 - 2.0)·10 7 m/s.
Beta rays represent a flow of electrons or positrons . This follows, in particular, from the fact that they have the same effect as cathode rays and have the same specific charge (e/m), measured when they move in electric and magnetic fields.
Gamma rays are short-wave electromagnetic radiation with a wavelength not exceeding 10 -2 nm and, therefore, are characterized by the highest photon energy E > 0.1 MeV.
Gamma radiation is not an independent type of radioactivity. It accompanies the processes of α- and β-decays and does not cause a change in the charge and mass number of nuclei. It has been established that γ-rays are emitted by daughter nuclei, which at the moment of their formation are excited and “drop” their energy in a time of 10 -13 – 10 -14 s.
3. What is the composition of the nucleus of an atom? How, using the periodic table D.I. Mendeleev, is it possible to determine the composition of the atomic nucleus of a particular chemical element?
4. What is the physics of the processes occurring during alpha and beta decays of nuclei?
With α - radioactivity, the nuclear charge decreases by 2 units (in units of proton charge) and the mass number - by 4 units. The decay product is placed in the periodic table two cells to the left of the original element. During b - decay, the mass number does not change, but the charge number increases by one - the element in the periodic table shifts one cell to the right.
5. What is the mechanism of the effect of radioactive radiation on matter?
As particles of radioactive radiation penetrate deep into the substance as a result of a series of subsequent collisions, the energy of the particles gradually decreases and, finally, when it reaches the level of thermal motion, ionization stops. In this case, the alpha particle attaches two electrons (from the free electrons present in every substance) and turns into a helium atom. The negative β-particle (electron) remains in a free state or is attached to any atom or ion of the substance. A gamma photon is absorbed by the electron with which it last collided.
6. What is the harmful effect of radioactive radiation on biological objects?
The harmful effects of nuclear radiation are associated with the ionization and excitation of atoms of living cells of the body due to the Compton effect, bremsstrahlung, photoelectric effect and some other effects. Individual components of a living cell are changed or destroyed by this ionization, and the products of decomposition begin to act as poisons. Examples of destruction in the body are the destruction of chromosomes, swelling of cell nuclei and the cells themselves, changes in the permeability of cell membranes, etc. The most sensitive cells are those of the bone marrow, lymph glands, oral cavity and intestines, genitals, hair follicles and skin.
The greater the ionizing ability of the particles, the less their penetrating ability. Thus, an α-particle, when traveling in air, produces up to 40 thousand pairs of ions on a path of 1 cm. A beta particle at the same distance produces 40–50 pairs of ions, and γ-photons – from 10 to 250 pairs of ions. In accordance with this, a thin layer of any substance, for example, a paper screen, can serve as protection against α-particles. Plexiglas or an aluminum screen several millimeters thick can serve as protection against β-radiation. To protect against γ-radiation, thick layers of earth, concrete or heavy metals are used, for example, a lead screen several centimeters thick.
7. What can you tell us about the prevalence of radioactive isotopes in nature?
In conclusion, we note that radioactive isotopes are widely used in medicine for therapeutic, diagnostic and research purposes. For example, radioactive cobalt is used to treat malignant tumors as a γ-emitter. Radioactive isotopes of phosphorus, emitting β-particles, are used to treat blood diseases, radioactive iodine () - to treat the thyroid gland.
8. Give the concepts of exposure and absorbed radiation doses, as well as their powers. In what units are they measured?
Dose rate (irradiation intensity) is the increment of the corresponding dose under the influence of a given radiation per unit of time. It has the dimension of the corresponding dose (absorbed, exposure, etc.) divided by a unit of time. The use of various special units is allowed (for example, Sv/hour, rem/min, mSv/year, etc.).
Radiation dose - in physics and radiobiology - a value used to assess the impact of ionizing radiation on any substances, tissues and living organisms.
Exposure dose
The main characteristic for the interaction of ionizing radiation and the environment is the ionization effect. In the initial period of development of radiation dosimetry, it was most often necessary to deal with X-ray radiation propagating in the air. Therefore, the degree of ionization of the air in X-ray tubes or devices was used as a quantitative measure of the radiation field. A quantitative measure based on the amount of ionization of dry air at normal atmospheric pressure, which is quite easy to measure, is called exposure dose.
Exposure dose determines the ionizing ability of X-rays and gamma rays and expresses the radiation energy converted into the kinetic energy of charged particles per unit mass of atmospheric air. Exposure dose is the ratio of the total charge of all ions of the same sign in an elementary volume of air to the mass of air in this volume.
The SI unit of exposure dose is the coulomb divided by the kilogram (C/kg). The non-systemic unit is the roentgen (R). 1 C/kg = 3876 RUR.
Absorbed dose
When expanding the range of known types of ionizing radiation and the areas of its application, it turned out that the measure of the impact of ionizing radiation on matter cannot be easily determined due to the complexity and diversity of the processes occurring in this case. An important one, which gives rise to physicochemical changes in the irradiated substance and leads to a certain radiation effect, is the absorption of the energy of ionizing radiation by the substance. As a result, the concept of absorbed dose arose. The absorbed dose shows how much radiation energy is absorbed per unit mass of any irradiated substance and is determined by the ratio of the absorbed energy of ionizing radiation to the mass of the substance.
The unit of measurement of absorbed dose in the SI system is the gray (Gy). 1 Gy is the dose at which 1 J of ionizing radiation energy is transferred to a mass of 1 kg. The extrasystemic unit of absorbed dose is the rad. 1 Gy=100 rad.
Equivalent dose (biological dose)
The study of individual consequences of irradiation of living tissues has shown that, with the same absorbed doses, different types of radiation produce unequal biological effects on the body. This is due to the fact that a heavier particle (for example, a proton) produces more ions per unit path in the tissue than a lighter particle (for example, an electron). For the same absorbed dose, the higher the radiobiological destructive effect, the denser the ionization created by the radiation. To take this effect into account, the concept of equivalent dose was introduced. The equivalent dose is calculated by multiplying the value of the absorbed dose by a special coefficient - the coefficient of relative biological effectiveness (RBE) or quality coefficient.
The SI unit of dose equivalent is the sievert (Sv). The value of 1 Sv is equal to the equivalent dose of any type of radiation absorbed in 1 kg of biological tissue and creating the same biological effect as the absorbed dose of 1 Gy of photon radiation. The non-systemic unit of measurement of equivalent dose is the rem (before 1963 - the biological equivalent of an x-ray, after 1963 - the biological equivalent of a rad - Encyclopedic Dictionary). 1 Sv = 100 rem.
Effective dose
Effective dose (E) is a value used as a measure of the risk of long-term consequences of irradiation of the entire human body and its individual organs and tissues, taking into account their radiosensitivity. It represents the sum of the products of the equivalent dose in organs and tissues by the corresponding weighting factors.
Some human organs and tissues are more sensitive to the effects of radiation than others: for example, at the same equivalent dose, cancer is more likely to occur in the lungs than in the thyroid gland, and irradiation of the gonads is especially dangerous due to the risk of genetic damage. Therefore, radiation doses to different organs and tissues should be taken into account with different coefficients, which is called the radiation risk coefficient. By multiplying the equivalent dose value by the corresponding radiation risk coefficient and summing over all tissues and organs, we obtain an effective dose reflecting the total effect on the body.
Weighted coefficients are established empirically and calculated in such a way that their sum for the entire organism is unity. The effective dose units are the same as the equivalent dose units. It is also measured in sieverts or rem.
Effective and equivalent dose- these are standardized values, that is, values that are a measure of damage (harm) from the effects of ionizing radiation on a person and his descendants [source not specified 361 days]. Unfortunately, they cannot be directly measured. Therefore, operational dosimetric quantities have been introduced into practice, unambiguously determined through the physical characteristics of the radiation field at a point, as close as possible to the standardized ones. The main operational quantity is the ambient dose equivalent (synonyms - ambient dose equivalent, ambient dose).
Ambient dose equivalent H*(d)- dose equivalent, which was created in the ICRU (International Commission on Radiation Units) spherical phantom at a depth d (mm) from the surface along a diameter parallel to the direction of radiation, in a radiation field identical to that considered in composition, fluence and energy distribution, but monodirectional and homogeneous, that is, the ambient dose equivalent H*(d) is the dose that a person would receive if he were at the place where the measurement is being taken. The unit of ambient dose equivalent is the sievert (Sv).
9. Characterize the effect of ionizing radiation on air under normal conditions, if the exposure dose rate is 1 R/s.
10. What are the measures to protect against radioactive radiation?
The shorter the contact time your body has with radioactive substances, the better for you and your health. If this is not yet possible, we take the following measures: do not leave the premises, do wet (namely wet!) cleaning 2-3 times a day;
· We shower as often as possible (especially after going outside), and wash things. Regular rinsing of the mucous membranes of the nose, eyes and throat with saline solution is not so important, since a much larger amount of radionuclides enters during breathing;
· to protect the body from radioactive iodine-131, it is enough to lubricate a small area of skin with medical iodine. According to doctors, this simple method of protection lasts for a month;
· if you have to go outside, it is better to wear light-colored clothes, preferably cotton and damp ones. It is recommended to wear a hood and a baseball cap on your head at the same time;
· in the first few days you need to be wary of radioactive fallout, that is, “lay low and sit out.”
The purpose of the lesson: to find out what the phenomenon of radioactivity is, what is the composition, nature and properties of radioactive radiation. To achieve an understanding of the meaning of the physical concept of “radioactive radiation”.
Literature and equipment:
- Myakishev G.Ya. Physics 11 – M.: Education, 2010
- Portrait of M. and P. Curie.
- Mendeleev table.
- Table “Electromagnetic radiation scale”.
- Projector.
- Laptop.
- Screen.
During the classes
Discovery of more natural radioactivity.
The words “radioactive radiation”, “radioactive elements”, “radiation” are known to everyone today. Many people probably also know that radioactive radiation serves people: in some cases they make it possible to make the correct diagnosis of a disease, and also treat dangerous diseases, increase the yield of cultivated plants, etc.
Controversy.
The phenomenon of radioactivity.
It is this phenomenon that will serve as the object of our conversation today.
What do you know about this phenomenon? What is your attitude towards him?
Controversy Generalization of the obtained data.
What is more: positive or negative from information about this phenomenon?
Negativity.
What do you think is the problem?
Why, despite all the troubles that accompany the phenomenon of radioactivity, do people still widely use it?
I propose to formulate the purpose of our lesson.
The goals and objectives are formulated by schoolchildren.
Purpose: To study the phenomenon of radioactivity and its significance for humans.
Now let’s formulate the tasks that serve as stages of our work.
1) Consider the concept of radioactivity.
2) Consider the types of radioactivity.
3) Familiarize yourself with the areas of application of radioactivity.
4) Determine the value of radioactivity for humans.
Solution to the problem.
To solve this problem, we will have to solve several problematic problems.
In order to solve our first task - to formulate a definition of the concept of “radioactivity” - we need to think about the meaning of the term itself. Let's try to reveal its etymology. What two bases does this word consist of?
Radio activity
“radiare” – lat. emit rays
Activity speaks for itself.
In what case does a substance, an atom, emit something?
If it falls apart.
Note the second meaning of the Latin word “radiare” – rays.
Radioactivity was discovered by the French scientist Henri Becquerel in 1896. He studied the glow of certain substances, in particular uranium salts (double sulfate of uranium and potassium), previously irradiated with sunlight.
Radioactivity is the spontaneous decay of atomic nuclei with the emission of elementary particles.
Students make messages.
This is how the scientist describes his experiments in his first speech.
Student Report No. 1:
“We wrap a bromogelatin Lumiere photographic plate with two sheets of black paper, very thick, such that the plate is not veiled by exposure to the sun during the day. Place a plate (uranium salt crystal) on a piece of paper outside and expose it all to the sun for several hours. When we then develop the photographic plate, we see that a black silhouette of this plate appears on the negative. If, however, between the plate and the paper we place a coin or a metal screen cut with an openwork pattern, we see an image of these objects appearing on the negative. The crystal plate in question emits rays that pass through paper, opaque to light, and distinguish silver salts.”
Student Report No. 2:
“Among the previous experiments, some were prepared on Wednesday 26 and Thursday 27 February, and since the sun appeared intermittently on those days, I mothballed the experiments, fully prepared, and returned the photographic plates to the dark, in a furniture box, leaving the uranium salt plates in place . In the following days the sun did not appear again. I developed the plates on March 1st, hoping to find weak images. The silhouettes, on the contrary, appeared with great intensity.”
A. Becquerel's father and grandfather studied luminescent substances.
“It was quite clear why the phenomenon of radioactivity was made in our laboratory, and if my father had been alive in 1896. He would be the one to do it.”
A. Becquerel, having discovered a new phenomenon, did not yet know (and could not know) what it was connected with, he only spoke of it as a “new order of phenomena.”
Students conclude: uranium salts spontaneously, without the influence of external factors, create some kind of radiation.
Properties of radioactive radiation. Discovery of radioactive elements.
Intensive studies of radioactive radiation began, with the aim of studying their properties and composition, and also to determine whether other elements emit similar radiation. The first studies were carried out by Becquerel himself, and then by M. Sklodowska-Curie and P. Curie, and Rutherford also did this.
Properties of radioactive radiation:
Act on a photographic plate,
Ionizes the air
Penetrates through thin metal plates
Complete independence from external conditions (lighting, pressure, temperature).
The main efforts in the search for new elements with the ability to spontaneously irradiate were made by M. and P. Curie. they discovered thorium, and then, after processing a huge amount of uranium ore, they isolated new chemical elements, which they called “polonium”, “radium” (radiant) (0.1 g of Radium in 1902)
What can this substance (radium) do?
E. Curie “Marie Curie” (p. 163)
The phenomenon of spontaneous radiation was called radioactivity by the Curies.
It was subsequently established. That all chemical elements with an atomic number greater than 83 are radioactive.
Lighter nuclei also have radioactive isotopes.
Student message “M. Curie’s contribution to the study of radioactivity.”
Physical nature of radioactive radiation.
Radioactive radiation has a complex composition.
Students read the description of the experience (textbook p. 308 Fig. 258) and fill out the table independently.
Properties of radioactive radiation (A.S. Enochovich Handbook of Physics and Technology p. 208 table 260.)
| α-λ teach | β-λ teach | γ-λ teach | |
| The speed of particles emitted from the nuclei of radioactive substances. | 14000–20000 km/s | 160000 km/s | 300000 km/s |
| Particle energy. | 4–9 MeV | from hundredths to 1–2 MeV | 0.2 – 3 MeV |
| The mass of one emitted particle. | 6.6*10 kg | 9*10 kg | 2.2*10 kg |
| Mileage (path traversed by a particle in a substance before stopping): in the air, in aluminum, in biological tissue. |
up to several hundred meters, in lead up to 5 cm permeate the human body. |
Radioactivity is the spontaneous, continuous disintegration of some natural and artificial elements, not amenable to any external influence, with the formation of new nuclei, during which these substances emit alpha, beta, and gamma radiation.
Fastening:
In the scientific literature, in newspapers and magazines, the concept of “radioactive radiation” is often found. What it is? What types of radioactive radiation do you know?
V. Mayakovsky “Conversation with the financial inspector about poetry”:
Poetry is like radium mining.
Per gram production,
During the years of labor.
You exhaust one word for the sake of
Thousands of tons of verbal ore.
With the research of which famous scientists can the poet’s work be compared?
Answer in writing the question: “Why, despite all the consequences, does humanity continue to actively use radioactivity?”
Because the significance is great for a person, and the consequences can be avoided with the right approach, use and lifestyle.
Read the famous physicist's words as he considered the results of his experiment of bombarding a sheet of gold with alpha particles. Give the name of the scientist and the year when he drew the conclusion from this experiment.